<gm:page title="Name" css="/css/g.css" class="googleTheme" onload="getName()" authenticate="true" >
  <div id="header" class="gm-app-header"/>
  <script>
    function getName() {
      var name = prompt("Please enter your name");
      document.getElementById("header").innerHTML = "Hello " + name;
    }
  </script>
</gm:page>